Topic 7 Flashcards
7.2 Suggest practical methods for determining the rate of a given reaction
Rate of reaction = amount of reactant used Time
Rate of reaction = amount of product formed Time
o Quantity of reactant or product can be measured by the mass in grams or by a volume in cm3
Units of rate of reaction may be given as g/s or cm3/s
o o
to measure reactant used: if the product is a gas, which will be given off, you can carry out the reaction on a set of weighing scales and measure how much mass is lost
to measure product formed: if the product is a gas, you can measure the volume of gas produced in a gas syringe
7.3 Explain how reactions occur when particles collide and that rates of
reaction are increased when the frequency and/or energy of collisions is
increased
Chemical reactions only occur when the reacting particles collide with enough energy, the minimum amount of energy required is called the activation energy.
● in order to increase the rate of a reaction, you need to increase the frequency/energy of collisions, so that more of them reach the activation energy
● this can be done by: increasing temperature, pressure, concentration, surface area or by using a catalyst
7.3 Explain how reactions occur when particles collide and that rates of
reaction are increased when the frequency and/or energy of collisions is
increased
● Chemical reactions only occur when the reacting particles collide with enough energy, the minimum amount of energy required is called the activation energy.
● in order to increase the rate of a reaction, you need to increase the frequency/energy of collisions, so that more of them reach the activation energy
● this can be done by: increasing temperature, pressure, concentration, surface area or by using a catalyst
7.4 Explain the effects on rates of reaction of changes in temperature,
concentration, surface area to volume ratio of a solid and pressure (on
reactions involving gases) in terms of frequency and/or energy of collisions
between particles
● Increasing the temperature increases the rate of reaction. As increasing temperature increases the kinetic energy of particles, so they collide more frequently and energetically.
● Increasing pressure in reacting gases increases the rate of reaction, as it increases the number of particles in a given volume so increases the frequency of collisions.
● Increasing concentration of reacting solutions increases the rate of reaction, as it increases the number of particles in a given volume and so increases the frequency of collisions.
● Increasing the surface area of solid reactants increases the rate of reaction, as it increases the frequency of collisions so increases the rate of reaction
Describe a catalyst as a substance that speeds up ROR
Catalysts are substances that speed up chemical reactions without being changed or used up during the reaction. They are the same and have the same mass at the end of the reaction.
Explain how the addition of a catalyst increase ROR
Catalysts decrease the activation energy; this increases the proportion of particles with energy to react, leading to more frequent successful collisions and so an increased rate of reaction
● Catalysts lower the activation energy by providing a different pathway for a chemical reaction that has a lower activation energy.
Recall that enzymes are biological catalyst
Enzymes act as catalysts in biological systems
● Yeast is the enzyme used in the production of ethanol as it is fermented from
sugars, ethanol is in alcoholic drinks
